The interest in alternative or renewable energy sources for greenhouse heating is currently high, owing to the large heating loads and the relatively high price of fossil fuels. Important alternative sources of energy are solar collectors, heat pumps, biomass and cogeneration systems. This study experimentally investigates greenhouse heating by biogas, solar and ground energy in Elazig, Turkey climate conditions. The greenhouse (6 m x 4 m x 2.10 m) heated by mentioned alternative energy sources was constructed, and then required heating load of the greenhouse was determined. For this purpose, biogas, solar and a ground source heat pump greenhouse heating system (BSGSHPGHS) with horizontal slinky ground heat exchanger was designed and set up. Experiments were conducted extensively during the winter period from November 2009 to March 2010. During the experiments, 2231.831 of gas production by biogas system is provided. The experiments that are required for the growth of many plants need temperature of 23 degrees C, and conceivable success has been achieved in reaching this value by built systems. As a result, different energy sources have been successfully tested for greenhouse heating. (C) 2013 Elsevier B.V. All rights reserved.